Introduction
Open Circuit Voltage (OCV) is a fundamental component of battery models. Accurate modeling of OCV is essential for accuracy of battery models as well as to optimize battery performance, longevity, and safety.
In this article, we deep dive into how TWAICE OCV Aging Modeling enables higher modeling accuracy and why important for simulations over lifetime of batteries.
What is OCV?
The open-circuit-voltage (OCV) describes the thermodynamic equilibrium voltage of the cell, referring to the voltage of the battery when it is not connected to a load or a charging device.
The specific shape of the OCV curve is defined by the material composition of the anode and cathode as well as the amount of accessible capacity in each electrode.
The relationship between OCV and SoC can be used to tune state-of-charge estimation algorithms in battery management systems.
Why OCV Aging is Important?
OCV aging refers to changes in the OCV curve as batteries age due to external stress factors such as temperature, charge cycles, and state of charge (SoC). These changes impact the accuracy of battery models over time.
Typically, when a battery ages, less of the battery’s available energy and power is available over time. If the OCV curve is not updated with aging, there is a risk of overestimating remaining capacity and energy, leading to issues related to system sizing. For example, a product may be designed assuming that the cells can perform according to their specifications (i.e., beginning-of-life performance). However, as the cells in this product age, they are generally unable to supply the same amount of energy and power. Ultimately, cells either need to be replaced earlier than expected or the product must be replaced entirely.
Figure 1: From left to right, exemplary Aging curves for Anode Potential (PHI-NE), Cathode Potential (PHI-PE), and the full cell OCV (Ucell).
When OCV is updated over the battery’s lifetime, it enables a better electrothermal performance simulation while the battery is aging, and therefore a better lifetime definition. This is crucial for optimizing the performance and longevity of batteries, as well as ensuring the safety and reliability.
Key Benefits of Modeling OCV Aging:
Improved Accuracy: Accounting for OCV aging ensures more reliable battery performance predictions, particularly as cells approach the end of their lifespan.
Optimized System Design: By updating OCV data, manufacturers prevent overestimations of remaining energy and capacity, reducing the risk of premature replacements or system failures.
Extended Battery Lifespan: Accurate simulations of electrothermal performance enable better definitions of battery lifetimes and more efficient maintenance strategies.
Integrating OCV aging in battery modeling with TWAICE
OCV aging over lifetime: TWAICE model simulate the change of the OCV curve with aging. By modeling the electrode potentials and their balances, we reconstruct the OCV and can output the anode and cathode open-circuit potentials separately. This results in a higher accuracy of the electric model, especially for aged cells. Furthermore, it enables the utilization of the updated OCV for tasks such as parameterizing state estimation filters (e.g., Kalman filters) for estimating state of charge and state of health.
Degradation Modes: Aging mechanisms such as SEI formation, lithium plating, and particle cracking are linked to OCV aging. TWAICE models include these mechanisms to provide a more precise representation of battery aging processes. Outputs such as Loss of Lithium Inventory (LLI) and electrode-specific degradation provide valuable insights into battery health.
Conclusion
OCV aging is a critical factor in understanding and predicting battery performance and degradation. By integrating OCV aging into its advanced simulation models, TWAICE delivers unparalleled accuracy, helping customers optimize battery designs, extend lifespans, and improve safety. TWAICE’s innovative approach empowers manufacturers and operators to make informed decisions and achieve better outcomes across the battery lifecycle.
Discover how TWAICE’s cutting-edge simulation models can transform your battery development process. Contact us today for a demo or consultation.